The present invention relates to infrared radiation detectors. Infrared detectors are often used to sense the presence of people in connection with home burglar alarm systems or automated room lighting systems. To prevent an intruder from escaping detection by a burglar alarm system, a detector must be able to detect radiation coming from anywhere within a wide field of view.
Unfortunately, with planar sensors, sensitivity drops as the angle between the radiation beam and a line normal to the plane increases. This is because the cross section of the sensor available for absorbing radiation decreases as the angle increases. One solution is to use a detector with several sensors fixed at different angles relative to each other in such a configuration where the sum of the sensors' narrow fields of view cover a larger solid angle. However, this complexity increases the cost of the detector, and applications which use infrared detectors are often cost-sensitive applications.